Giardia Duodenalis: The Double-Edged Sword of Immune Responses in Giardiasis

Exp Parasitol. 2010 Nov;126(3):292-7. doi: 10.1016/j.exppara.2010.06.014. Epub 2010 Jun 18.


Giardiasis is one of the most common intestinal protozoan infections worldwide. The etiological agent, Giardia duodenalis (syn. Giardia lamblia, Giardia intestinalis), is a flagellated, binucleated protozoan parasite which infects a wide array of mammalian hosts (Adam, 2001). The symptoms of giardiasis include abdominal cramps, nausea, and acute or chronic diarrhea, with malabsorption and failure of children to thrive occurring in both sub-clinical and symptomatic disease (Thompson et al., 1993). Infections are transmitted by cysts which are excreted in the feces of infected humans and animals. Human giardiasis is distributed worldwide, with rates of detection between 2-5% in the developed world and 20-30% in the developing nations (Farthing, 1994). There is significant variation in the outcome of Giardia infections. Most infections are self-limiting, although re-infection is common in endemic areas and chronic infections also occur. Moreover, some individuals suffer from severe cramps, nausea and diarrhea while others escape these overt symptoms. This review will describe recent advances in parasite genetics and host immunity that are helping to shed light on this variability.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Adaptive Immunity
  • Animals
  • Antibodies, Protozoan / immunology
  • Disease Models, Animal
  • Giardia lamblia / genetics
  • Giardia lamblia / immunology*
  • Giardiasis / epidemiology
  • Giardiasis / immunology*
  • Giardiasis / prevention & control
  • Humans
  • Immunity, Innate
  • Mast Cells / immunology
  • Protozoan Vaccines


  • Antibodies, Protozoan
  • Protozoan Vaccines